Journal of the Civil Engineering Forum

Effect of Relative Density Variation on The Effectiveness of Fly Ash in Stabilization of Sandy Soils for Liquefaction Mitigation

Yunan Yakuta Wangsawitana — 2026-05-04

Indonesia is highly vulnerable to earthquakes that can trigger soil liquefaction, particularly in coastal regions where saturated sandy soils with low relative densities are prevalent. This study investigated the influence of varying Class C fly ash contents (5%, 10%, and 15%), relative densities (50%, 70%, and 90%), and curing periods (7 and 14 days) on the unconfined compressive strength of fully saturated sandy soils as a liquefaction mitigation approach. The methodology included physical soil characterization, sample preparation with specific fly ash and relative density variations, and unconfined compressive strength testing after the curing period. The results demonstrated that increasing the fly ash content, relative density, and curing time significantly enhanced the strength of the samples. The highest strength occurred at 15% fly ash and 90% relative density, with 426.22 kPa (7 days) and 438.57 kPa (14 days). The most notable improvement occurred with an increase in fly ash content from 5% to 10% and relative density from 50% to 70%. Fly ash was more effective at enhancing the strength of sandy soil by promoting interparticle cementation, whereas excessive compaction tended to disrupt the soil structure and generate fine particles that reduced cohesion, as evidenced by the UCS test results and SEM observations. The most significant strength gain between 7 and 14 days was observed at 50% relative density and 5% fly ash, with a twofold increase. The combination of 10% fly ash and 70% relative density was optimal for field implementation, as it yielded strength values exceeding the liquefaction resistance thresholds, while maintaining practical compaction levels and material efficiency. A comparative cost assessment considering materials, labor, equipment, and construction time is recommended to evaluate the practical feasibility of fly ash stabilization relative to alternative ground improvement methods for Indonesian projects.

Real-time Application and Statistical Evaluation of Reservoir Operating Rules Under Inflow Uncertainty in Monte Carlo Simulations

Muhammad Mujiburrakhman — 2026-06-18

Reservoir Operating Rules (ROR) have been well-known in Indonesia as guidelines for reservoir operation that comprise the release rules and rule curves derived from the dependable inflow time series in dry, normal, and wet conditions. However, likely because of the incoherence of the original application concept of ROR, the real performance of ROR in reservoir operation has so far remained unclear. This paper proposes a practical application concept of ROR and evaluates the performance of its implementation for annual storage conservation and periodic demand satisfaction under inflow uncertainty in the integrated system of Segawe Regulating Weir, Wonorejo Multipurpose Dam, and Tiudan Regulating Dam. The release rules for the three hydraulic structures were integrated into a unified “Wonorejo ROR”throughoptimization of water allocation over 36 ten-day operational periods. The performance of the application of Wonorejo ROR was evaluated based on several operational success and failure events in Monte Carlo simulations, for which 1,000 years of unique and independent synthetic inflow time series were generated from the Thomas–Fiering model. Under the application concept of ROR, the release decisions for the three hydraulic structures were made in real-time solely based on the actual water level of Wonorejo Reservoir and the rule curves of Wonorejo ROR. For comparative purposes, the Monte Carlo simulations were carried out to evaluate two alternatives of Wonorejo ROR, namely ROR-D65 and ROR-D80, which had different dry inflow exceedance probabilities. Based on the specified events in the Monte Carlo simulations, ROR-D65 and ROR-D80 resulted in reliabilities of 76.4% and 81.3% for annual storage conservation, and the lowest reliabilities of 73.9% and 52.4% for periodic demand satisfaction, respectively. In addition, other reservoir operational performancesandacomprehensive interpretation oftheproposed applicationconcept of ROR arepresented in this paper.

Analyzing Trends and Framework Models for Autonomous Vehicle Transition Strategies

Cintia Nurliyana — 2026-07-01

The shift from traditional human-driven to autonomous vehicles represents a transformation that is not merely technological, but also social. Currently, the deployment of autonomous vehicles remains largely at level where the human driver continues to be the primary decisionmaker. However, this dynamic is expected to change significantly as higher levels of autonomy are achieved. This study aims to identify the impacts that occur during process transition through emerging trends and theoretical lens of transition studies. The initial stage involved mapping trends in Autonomous Vehicle (AV) research to identify key related topics. This study uses bibliometric analysis of 82 key articles selected through a screening process in a systematic review. VOSviewer and CiteSpace were employed to map the research landscape, identify dominant topics, and trace the evolution of AV studies over time. The analysis highlights both well-established research areas and underexplored gaps. Furthermore, the articles were classified into categories based on transition study dimensions and key actors involedinvolved in facilitating a successful transition. The findings reveal a dominant research focus on users, human factors, and mobility behavior, whereas studies concerning vulnerable road users and the industry transition remain limited. To address this gap, this study investigates the socio-technical factors arising from the identified trends and transition studies while also exploring the roles of key stakeholders. This approach aims to achieve a more balanced perspective. Specifically, the study proposes a novel framework that connects critical actors with core socio-technical dimensions to support a sustainable autonomous ve-hicle transition. This research thus provides a strategic framework designed to guide and accelerate the shift toward autonomous mobility.